System and method for heating water

ABSTRACT

A system for heating a liquid, such as water, the system including a collector and a storage tank, wherein the collector and the storage tank are fluidly coupled together via a manifold. The collector includes a plurality of heat pipes which extend into the manifold. Solar energy is absorbed by the heat pipes and passed to liquid in the manifold, which in turn, is passed to the storage tank.

FIELD OF THE INVENTION

The present invention relates to systems and methods for heating aliquid, such as water. In particular, the invention relates to systemsand methods involving use of thermosiphoning and/or heat pipes.

BACKGROUND

Thermosiphoning solar systems have conventionally consisted of acollector and a water tank for storing hot water. The hot water tank islocated above the collector. As water in the collector is heated, itexpands, lowering its density and causing it to rise up through anoutlet at the top of the collector and into the hot water tank throughan inlet generally provided near the top thereof. At the same time,colder, more dense water is drawn into an inlet at the bottom of thecollector either from an outlet generally positioned at the bottom ofthe hot water tank or from an alternative source, such as the mainswater supply, another tank, etc.

US 2006/0219237 A1 describes a thermosiphoning system with side mountedstorage tanks. The system includes a substantially planar collector thathas a plurality of heat exchange channels (e.g. small diameter plastictubes) that are positioned next to one another in a parallelrelationship. Headers (e.g. large diameter plastic pipes) are providedat the top and bottom of the collector and storage tanks (e.g. largediameter plastic pipes) are provided on either side of the collector.

US 2006/0219237 A1 differs from earlier systems in that tanks areprovided either side of the collector as opposed to being above thecollector. As liquid is heated in the collector by solar power, it movesupwards towards the header at the top of the collector and then into aninlet provided at the top of each of the storage tanks. Water from thebottom of the storage tank may enter through one or more inlets in theheader at the bottom of the collector such that water circulates throughthe system. Hot water may be utilized by pumping it through an outletprovided in the header at the top of the collector, or through outletsprovided at the tops of the storage tanks. This water may be replenishedusing an inlet provided in the header at the bottom of the collectorthat is coupled to a water source such as a mains pipe.

Whilst US 2006/0219237 A1 takes some advantage of thermosiphoningprinciples, pumps are still required to move hot water to where it isrequired, which expend electrical energy and complicate the system.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved system and/ormethod for heating a liquid, such as water, or at least to provide auseful choice.

According to a first aspect of the invention, there is provided a systemfor heating a liquid, such as water, the system comprising a collectorand a storage tank, wherein the collector and the storage tank are eachsealably coupled to a manifold.

Preferably, the collector comprises a heat pipe. More preferably, thecollector comprises a plurality of heat pipes.

Preferably, the heat pipes are arranged to be substantially parallel.

Preferably, each heat pipe comprises an at least partially evacuatedtube that houses a first portion of a sealed, preferably copper, risertherein.

Preferably, each said at least partially evacuated tube is an at leastpartially evacuated glass tube.

Preferably, each said at least partially evacuated tube has first andsecond ends.

Preferably, each said at least partially evacuated tube is coupled tothe manifold proximate the first end thereof, and the second end isdistal therefrom.

Preferably, a second portion of each said riser extends out of the atleast partially evacuated tube at the first end thereof and into themanifold. Preferably, each said second portion of the riser is in theform of a bulb.

Preferably, the second portion of each said riser is oriented above therespective first portion thereof.

Preferably, sealing means, such as a plug, is provided proximate thefirst end of each said at least partially evacuated tube so that atleast a partial vacuum is maintained therein.

Preferably, each said sealing means sealably engages an inside wall of acorresponding said at least partially evacuated tube and has an aperturefor sealably receiving and holding a corresponding said riser.

Preferably, each said riser contains a liquid, such as water. Morepreferably, each said riser contains distilled water or alcohol.

Preferably, the manifold comprises a conduit having a preferablysubstantially square cross-section.

Preferably, the manifold comprises a plurality of apertures.

Preferably, each of the apertures is adapted to allow the bulb of acorresponding said riser to pass therethrough such that the bulbs aresituated inside the conduit.

Preferably, the manifold comprises an inlet and an outlet.

Preferably, the storage tank comprises a hot water cylinder that isoriented such that its axis is substantially horizontal.

Preferably, the manifold outlet is fluidly coupled to a first storagetank inlet. Preferably, the first storage tank inlet is oriented abovethe manifold outlet.

Preferably, the manifold inlet is fluidly coupled to a first storagetank outlet. Preferably, the first storage tank outlet is oriented abovethe manifold inlet.

Preferably, the storage tank comprises a second storage tank inletadapted to receive liquid from an external source, such as the watermains.

Preferably, the storage tank comprises a second storage tank outlet.Preferably, the second storage tank outlet is adapted to enable users todraw hot liquid from the storage tank, as required.

Note that the first and second storage tank inlets and the first andsecond storage tank outlets are used to denote inlets and outlets of thesame storage tank (i.e., the first and second storage tank inlets arefirst and second inlets of the same storage tank).

Preferably, the storage tank comprises auxiliary heating means, such asan electrical heating element. The auxiliary heating means may be usedto provide additional heat to liquid in the storage tank such as attimes when there is a high demand on the system or when there is littleor no solar power available (e.g. at night or during cloudy conditions).

Where an electrical heating element is used, preferably, the storagetank comprises an anode for preventing corrosion to the lining of thestorage tank due to galvanic action or electrolysis.

Preferably, the system comprises remote heating means, such as awetback, which may be used to generate additional hot liquid.

Preferably, the remote heating means comprises an inlet and an outlet.

Preferably, the storage tank comprises a generally serpentine conduit orcoil that has an inlet and an outlet. Preferably, the inlet and theoutlet are provided proximate a wall of the storage tank and the coil issubstantially housed within the storage tank.

Preferably, the remote heating means outlet is fluidly coupled to thecoil inlet, such that liquid heated by the remote heating means may flowthrough the coil and thereby provide heat to the liquid that is held inthe storage tank outside of the coil.

Preferably, the remote heating means inlet is fluidly coupled to thecoil outlet so that liquid may return to the remote heating means as itcools down and be reheated. Alternatively, the remote heating meansinlet may be adapted to receive liquid from an external source so thatliquid leaving the remote heating means is replenished as opposed tosimply circulating between the coil and the remote heating means.

Preferably, the coil outlet is oriented below the coil inlet.

Preferably, the coil inlet comprises a valve, such as a ball valve,which enables excess pressure to be relieved.

According to second through fourth aspects there are respectivelyprovided a collector, a manifold or a storage tank adapted for use inthe system of the first aspect.

A fifth aspect of the invention is to use of the system of the firstaspect and/or use of one or more apparatus of the second through fourthaspects for heating a liquid.

According to a sixth aspect, there is provided a method of heating aliquid, such as water, the method comprising providing a solar powercollector in thermal communication with a manifold and the manifold influid communication with a storage tank such that, in use, solar powerreceived by the collector causes heat to be transferred to the manifoldand to any liquid therein, and the heated liquid then passes to thestorage tank by thermosiphoning.

Preferably, the method comprises providing an electoral heating elementin the storage tank, such that, in use, liquid may be heated therein.

Preferably, the method comprises thermally coupling the storage tank toan external heating means, such as a wetback.

Further aspects of the invention, which should be considered in all itsnovel aspects, will become apparent to those skilled in the art uponreading the following description which provides at least one example ofa practical application of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will be described below by wayof example only and without intending to be limiting with reference tothe following drawings, in which:

FIG. 1 is a schematic perspective view of an embodiment of a systemaccording to the invention;

FIG. 2 is a perspective view of an embodiment of the system of theinvention, similar to that of FIG. 1, with a portion removed to aidunderstanding;

FIG. 3 is a cross-sectional side view of a portion of the system of FIG.1 or 2;

FIG. 4 is a cross-sectional view of a storage tank, such as for use withthe system of FIGS. 1 and/or 2;

FIG. 5 is an alternative cross-sectional view of the storage tank ofFIG. 4;

FIG. 6 is a schematic diagram of an alternative embodiment of the systemof the invention;

FIGS. 7A-7C show embodiments of fixings that may be used withembodiments of the invention; and

FIG. 8 is a flow diagram of an embodiment of the method of theinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 show system 1 according to slightly varying embodiments ofthe invention, which do not materially differ. System 1 includes acollector 10, a manifold 12 and storage tank 14. Storage tank 14 may bereferred to as a hot water cylinder and is abbreviated hereinafter tohwc.

Collector 10 comprises a plurality of heat pipes 16 which are preferablyarranged substantially parallel to each other to form a preferablysubstantially planar collector of solar power. FIG. 3 is across-sectional side view of a heat pipe 16 of collector 10 and manifold12 that shows the internal configuration thereof and the presentlypreferred manner in which they are coupled together. Heat pipe 16comprises tube 30 which houses a first portion 31 of sealed or closed,preferably copper, riser 32 therein. Tube 30 is preferably an at leastpartially evacuated glass tube so that the sun's rays may passtherethrough and impinge on riser 32, thereby causing riser 32 to heatup, but heat loss by conduction from riser 32 is reduced.

Riser 32 is at least partially filled with a liquid, preferably alcohol,so that as riser 32 heats up, this heat is transferred to the liquidtherein. Moreover, liquid in first portion 31 of riser 32 heats up andmay vaporise. As it does so, it moves towards second portion 33 of riser32, second portion 33 preferably being in the form of a bulb and abovefirst portion 31.

Manifold 16 comprises a conduit having a preferably substantially squarecross-section, although other cross-sections, including generallycircular, are also within the scope of the invention. Manifold 16comprises a plurality of apertures 34, each of which is adapted toreceive and sealably engage a corresponding tube 30. Preferably,manifold 12 sealably engages tube 30 at, or at least proximate to, afirst end 35 thereof so that tube 30 does not significantly extend intothe space inside manifold 12 and inhibit flow of liquid therethrough, aswill be described in more detail below.

Preferably, second portion 33 of each riser 32 extends out of tube 30 atfirst end 35 thereof and into manifold 12. Sealing means, such as plug36, is provided proximate first end 35 of each said at least partiallyevacuated tube so that at least a partial vacuum is maintained insidetube 30. Each plug 36 sealably engages an inside wall of a correspondingtube 30 and has an aperture for sealably receiving and holding acorresponding riser 32. Preferably, each plug 36 is configured as thesole support for the corresponding riser 32.

The extension of risers 32 into manifold 12 enables the transfer of heatfrom first portion 31 of riser 32 to second portion 33 and then to theinside of manifold 12. The configuration of second portion 33 of riser32 as a bulb improves the rate of heat exchange with a liquid that maybe present in manifold 12. Insulation 37 may be provided to reduce heatloss from manifold 12 to the surroundings.

Referring back to FIGS. 1 and 2, manifold 12 comprises inlet 38 andoutlet 39 which enable liquid to enter through inlet 38, flow throughmanifold 12 and exit through outlet 39. During passage of the liquidthrough manifold 12, the temperature of the liquid rises as the liquidis heated by the bulbs of risers 32.

Hwc 14 is preferably substantially cylindrical and oriented such thatits axis is substantially horizontal. Hwc 14 is fluidly coupled tomanifold 12 such as by conduits or pipes so that liquid, generallywater, may flow therebetween. In particular, manifold outlet 39 isfluidly coupled to first storage tank inlet 40 and manifold inlet 38 isfluidly coupled to first storage tank outlet 41.

Preferably, first storage tank inlet 40 is oriented above manifoldoutlet 39. While not such in such a configuration in the Figures,preferably, the first storage tank inlet 40 is located towards the topof hwc 14. Preferably, first storage tank outlet 41 is oriented abovemanifold inlet 38.

Preferably, hwc 14 comprises second storage tank inlet 42 (see FIG. 2)which is adapted to receive liquid from an external source, such as thewater mains. Hwc 14 also comprises second storage tank outlet 43. Secondstorage tank outlet 43 is adapted to enable users to draw hot liquidfrom hwc 14, as required. For example, second storage tank outlet 43 maybe fluidly coupled to one or more hot water taps (not shown) usingappropriate piping. As hot liquid is drawn off through second storagetank outlet 43, liquid stored in hwc 14 is replenished through secondstorage tank inlet 42.

Operation of the invention will now be described. Rays from the sun passthrough tubes 30 and heat risers 32 and the liquid therein. As theliquid in risers 32 heats, it expands and may vaporise. The heatedliquid and/or vapours become more buoyant and rise into second portion33 of riser 32 inside manifold 12 i.e., the bulb. A liquid, generallywater, is present in manifold 12 and is heated as it comes into contactwith the bulbs. As the liquid in the manifold 12 heats up, it expandsand passes out of manifold outlet 39 and into hwc 14 through firststorage tank inlet 40. If there is no external draw operating on system1 through second storage tank outlet 43 (e.g. no one is running a hotwater tap), cooler liquid from the bottom of hwc 14 is drawn intomanifold 12 through manifold inlet 38, where it is in turn heated,thereby circulating the liquid between manifold 12 and hwc 14. If thereis an external draw on system 1, cooler liquid from an external source,such as the water mains, enters hwc 14 via second storage tank inlet 42so that as hot liquid is drawn from system 1, it is replenished. Theliquid in hwc 14 may then pass to manifold 12 to be heated.Alternatively, the external source of liquid may be fluidly coupled tomanifold 12 as opposed to hwc 14. Thus, liquid may be replenished inmanifold 12 as opposed to hwc 14.

Due to the particular vertical arrangements of each of the components ofsystem 1, system 1 may operate on the basis of thermosiphoning and doesnot require the use of pumps. However, the present invention does notpreclude the use of pumps in combination with any of the embodimentsthereof.

Preferably, hwc 14 comprises auxiliary heating means, such as electricalheating element 45. Electrical heating element 45 may be used todirectly provide additional heat to liquid in hwc 14 such as at timeswhen there is a high demand on system 1 or when there is little or nosolar power available (e.g. at night or during cloudy conditions).Electrical heating element 45 may comprise, or be coupled to, athermostat so that heating by electrical heating element 45 iscontrolled to prevent overheating. In embodiments including electricalheating element 45, preferably, hwc 14 comprises anode 46 for preventingcorrosion to the lining of the storage tank due to galvanic action orelectrolysis. Anode 46 may be comprised of magnesium or aluminium andpreferably has a higher potential than the material it is protecting,namely a lining of hwc 14, which acts as a cathode. Anode 46 issacrificed or dissolved in order to prevent corrosion of hwc 14.

Electrical heating elements and anodes are well known in the art and theskilled man would be able to modify and/or select an appropriate elementand/or anode depending on the desired application. The invention istherefore not limited to the particular type or configuration of elementand/or anode shown but it is intended to include any such modifications.

As shown in FIGS. 1 and 2, hwc 14 comprises coil 50. Coil 50 is shown inmore detail in FIGS. 4 and 5. Coil 50 comprises a generally serpentineconduit having inlet 51 and outlet 52. Preferably, inlet 51 and outlet52 are provided proximate a wall of age to receive 14 and coil 50 iscontained within hwc 14. Coil inlet 51 is preferably arranged to beabove coil outlet 52. Each serpentine coil of coil 50 comprises asubstantially linear section followed by an arcuate section and thenanother substantially linear section. Each linear section, as one movesfrom coil inlet 51 to coil outlet 52, has a downward gradient. In apreferred embodiment, each linear section has a length of between 2 and2.5 m and preferably falls by between 6 and 12 millimetres over thatlength, so as to facilitate thermosiphoning. Coil 50 may be securedusing plates 47 and fixings 48 (e.g. nuts and bolts).

Referring to FIG. 6, coil 50 is fluidly coupled to a remote heatingmeans, such as wetback 60. Wetback 60 preferably comprises a furnacewhich may be used to remotely heat a liquid, such as by burning solidfuel. Wetback 60 comprises outlet 61 and inlet 62. Wetback outlet 61 isfluidly coupled to coil inlet 51, such that liquid heated by wetback 60may flow through coil 50 and thereby provide heat to the liquid that isheld in hwc 14. Coil outlet 52 is preferably fluidly coupled to wetbackinlet 62 so that after the liquid has passed through coil 50 and cooleddown due to its use in heating the relatively cooler liquid inside hwc14, it is recirculated to wetback 60 for reheating. Additionally oralternatively, wetback 60 may be adapted to receive liquid from anauxiliary source, such as the water mains, so that liquid leavingwetback 60 is otherwise replenished.

Preferably, coil inlet 51 is situated at a height greater than that ofwetback outlet 61. Preferably, coil outlet 52 is at a height greaterthan that of wetback inlet 62. Preferably, wetback outlet 61 is abovewetback inlet 62.

A pressure relief valve or vent, such as ball valve 63, may be used torelieve excess pressure proximate coil inlet 51.

Also shown in FIG. 6 is the connection of system 1 to external liquidsupply 65, such as the water mains. Other supplies of liquid may be usedas would be apparent to one of skill in the art, such as reservoirs,separate containers or tanks, wells etc. External liquid supply 65 isfluidly coupled to second storage tank inlet 42, such as by suitablepiping. External liquid supply 65 may further be coupled to wetback 60.Preferably, this coupling comprises isolation valves 66 with pressurereducing valve 67 fluidly coupled therebetween. This arrangement ofvalves enables flow of liquid in the correct direction and also allowsfor the relief of any excess pressure.

FIGS. 7A through 7C show various fittings that may be used with system1. Referring to FIG. 7A, there is shown tray 70. Tray 70 is adapted suchthat hwc 14 may be seated thereon. Tray 70 may include tray outlet 71which is adapted to allow liquid leaking from hwc 14 and the variousinlets and outlets thereof to be captured in tray 70 and passed throughtray outlet 71 to an appropriate drain.

FIG. 7B shows means 72 for retaining hwc 14 in position. Means 72preferably comprises an angled bracket. Means 72 preferably works incombination with retaining means 73 of FIG. 7C, such that rotational orsliding movement of hwc 14 is prevented. Thus, hwc 14 is held betweenmeans 72 and first face 74 of retaining means 73. Second face 75 ofretaining means 73 is preferably adapted to fixedly hold manifold 12 inposition.

Various elements of system 1 may be provided with insulation. Forexample, hwc 14 may be provided with heat insulation as would beapparent to one of skill in the art.

According to preferred embodiments of the invention, collector 10,manifold 12 and hwc 14 are adapted for installation outside, such as onthe roof of a building. However, according to an alternative embodiment,hwc 14 may be installed inside a building, such as in the roof cavitythereof, with the conduits from manifold 12 appropriately extended.Thus, at least hwc 14 may be remotely located from collector 10 and/ormanifold 12. Preferably, the generally upward gradient is maintainedfrom the free ends of heat pipes 16 to manifold 12 and then to firststorage tank inlet 40.

A preferred method of the invention is set out in FIG. 8. The methoddepends on whether or not there is solar power available, or moreover,whether there is sufficient solar power available. If there is, theliquid in heat tubes 16 is heated and the risers then heat the liquid inmanifold 12. As the liquid is heated in manifold 12, it expands andbecomes more buoyant, causing it to pass to hwc 14. Then, depending onwhether there is an external drain on hwc 14, such as through use of ahot water tap coupled to second storage tank outlet 43, liquid from anexternal source, such as the water mains, may pass into hwc 14. Ineither case, colder liquid from hwc 14 passes to manifold 12 through amanifold inlet 38 as warmer liquid exits through manifold outlet 39.

If there is not sufficient solar power available, one or both of twoadditional methods may be used. Firstly, electrical heating element 45may be switched on to heat liquid in hwc 14 as required. Alternativelyor additionally, wetback 60 may be activated to heat liquid therein,such as by using a furnace. The heated liquid expands and becomes morebuoyant, causing it to rise to coil inlet 51. The liquid flows throughcoil 50 until it reaches coil outlet 52 where it is passed back towetback 60 for reheating. As the liquid flows through coil 50, it heatsliquid held in hwc 14.

It should be noted that any combination of the three methods of heatingmay be used. For example, in times of high demand, all three methods maybe used simultaneously.

Dimensions included in any of the Figures are preferred dimensions andare not intended to be limiting.

It should be noted that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications may be madewithout departing from the spirit and scope of the present invention andwithout diminishing its attendant advantages. It is therefore, intendedthat such changes and modifications be included within the presentinvention.

1. A system for heating a liquid, such as water, the system including acollector and a storage tank, wherein the collector and the storage tankare fluidly coupled together via a manifold.
 2. The system of claim 1,wherein the collector includes a plurality of heat pipes.
 3. The systemof claim 2, wherein the heat pipes are arranged to be substantiallyparallel to one another.
 4. The system of claim 2 or claim 3, whereineach heat pipe includes an at least partially evacuated tube that housesat least a first portion of a sealed riser therein.
 5. The system of anyone of claims 2 to 4, wherein at least a portion of each heat pipeextends into the manifold.
 6. The system of claim 5 when dependent onclaim 4, wherein the at least a portion of each heat pipe that extendsinto the manifold comprises a second portion of the respective riser. 7.The system of claim 6, wherein the second portion of each riser is inthe form of a bulb.
 8. The system of claim 6 or claim 7, wherein thesecond portion of each said riser is configured to be oriented above therespective first portion thereof when in use.
 9. The system of any oneof claims 2 to 8, wherein the manifold comprises a conduit having asubstantially constant cross-section and a plurality of apertures in atleast one wall thereof, each of the apertures being configured toreceive a respective one of the plurality of heat pipes, such that aportion thereof is located inside the manifold.
 10. The system of anyone of the preceding claims, wherein the storage tank comprises a hotwater cylinder that is oriented such that its major axis issubstantially horizontal.
 11. The system of any one of the precedingclaims, wherein the manifold comprises an inlet and an outlet, whereinthe manifold outlet is fluidly coupled to a first storage tank inlet andthe manifold inlet is fluidly coupled to a first storage tank outlet.12. The system of claim 11, wherein the first storage tank inlet isoriented above the manifold outlet and the first storage tank outlet isoriented above the manifold inlet.
 13. The system of 11 or claim 12,wherein the storage tank comprises a second storage tank inlet adaptedto receive liquid from an external source.
 14. The system of any one ofclaims 11 to 13, wherein the storage tank comprises a second storagetank outlet for enabling hot liquid to be drawn off from the storagetank.
 15. The system of any one of the preceding claims, wherein thestorage tank comprises auxiliary heating means.
 16. The system of anyone of the preceding claims, wherein the system comprises remote heatingmeans for generating hot liquid, the remote heating means having aninlet and an outlet.
 17. The system of claim 16, wherein the remoteheating means comprises a wetback.
 18. The system of claim 16 or claim17, wherein the storage tank comprises a generally serpentine conduit orcoil housed within the storage tank and having an inlet and an outlet.19. The system of claim 18, wherein the remote heating means outlet isfluidly coupled to the coil inlet, such that, in use, liquid heated bythe remote heating means flows through the coil and provides heat toliquid held in the storage tank outside of the coil.
 20. The system ofclaim 19, wherein the remote heating means inlet is fluidly coupled tothe coil outlet.
 21. Preferably, the coil outlet is oriented below thecoil inlet.
 22. A collector configured for incorporation in the systemof any one of the preceding claims.
 23. A manifold configured forincorporation in the system of any one of claims 1 to
 21. 24. A storagetank configured for incorporation in the system of any one of claims 1to
 21. 25. A method of heating a liquid, such as water, the methodcomprising providing a solar power collector in thermal communicationwith a manifold and the manifold in fluid communication with a storagetank such that, in use, solar power received by the collector causesheat to be transferred to the manifold and to any liquid therein, andthe heated liquid then passes to the storage tank by thermosiphoning.26. The method of claim 25, comprising providing an electrical heatingelement in the storage tank, such that, in use, liquid may be heatedthereby.
 27. The method of claim 25 or claim 26, comprising thermallycoupling the storage tank to an external heating means.